Upgrade eslint-plugin-matrix-org to 1.2.1

This upgrade came with a number of new lints that needed to be fixed across the code base. Primarily: explicit return types on functions, and explicit visibility modifiers on class members.

src/otel/OTelCallMediaStreamTrackSpan.ts

@@ -1,3 +1,19 @@
+/*
+Copyright 2023 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 import { TrackStats } from "matrix-js-sdk/src/webrtc/stats/statsReport";
 import opentelemetry, { Span } from "@opentelemetry/api";
 
@@ -8,8 +24,8 @@ export class OTelCallMediaStreamTrackSpan {
   private prev: TrackStats;
 
   public constructor(
-    readonly oTel: ElementCallOpenTelemetry,
-    readonly streamSpan: Span,
+    protected readonly oTel: ElementCallOpenTelemetry,
+    protected readonly streamSpan: Span,
     data: TrackStats
   ) {
     const ctx = opentelemetry.trace.setSpan(